1. Field of the Invention
The present invention relates to a chill roll for cooling of printing webs, and more particularly, pertains to a chill roll with an outer roll rotating about an inner roll. Coolant is distributed evenly along the interior space between the inner and outer roll, and circulates circumferentially between the rolls to effect a uniform heat transfer across the roasting roll.
2. Description of the Prior Art
Conventional chill rolls used in the printing industry have provided for cooling of a web by passing the web over a chill roll in an effort to reduce the temperature of the web, such as a printed web, to retard ink smearing, and to reduce web temperature before it is wound on a roll.
Coolant was traditionally introduced into one side of the roll whereupon that end of the roll provided for cooling of the web adjacent to the coolant introduction area. As the coolant proceeded to the opposite end of the chill roll, the coolant temperature, as well as the web temperature across the web, increased so that the exhaust end of the roller was warmer than the introduction end of the roller. The net effect was that one edge portion of the web was cooled quite well, but the opposing edge portion was cooled substantially less due to the temperature gradient differential across the chill roll. Other existing chill roll designs featured coolant passages which were located between the outer roll shell and an inner drum, and spiraled from one side of the roll to the other side. Still other existing chill roll structures had outer and inner drums which were rotated together, and as the B coolant traveled across the roll, the coolant was heated by the web so that a temperature differential still existed between the roll surface on leaving and entering the ends.
Prior art chill rolls merely pumped coolant into one end of the roll and simply forced it from the opposing end, which caused the area of the roll adjacent to the inlet to cool effectively. When the coolant picked up heat from the roll, the temperature of the area of the roll adjacent to the outlet end was much warmer than the area adjacent to the inlet. This temperature gradient across the roll would cause the web temperature to be variable in an increasing temperature differential, as well as across the roll and across the web.
Other chill roll designs depended upon an excessive coolant flow to maintain an improved and more constant temperature differential across the chill roll. The greater the flow, the smaller the temperature differential across the roll. The present invention does not require increased coolant flow to maintain a low temperature differential because there is no differential. The same temperature exists across the roll at any given roll tangent.
The present invention overcomes the disadvantages of the prior art devices by providing a chill roll which distributes coolant in an even and uniform fashion along and across the entire length of the chill roll interior so that heat transfer is accomplished circumferentially around and about an annular space and passage between an outer rotating chill roll and a stationary roll assembly Heat transfer is further enhanced by turbulence inducer bars causing turbulence in the coolant flow between the stationary roll and the rotary roll.